Explanation:
A thin piece of string has lower force than of a heavy load.
When the load is being lifted, the force exerted by the load is much more greater than the string, which eventually hits our hands.
For example, a heavy bag. You tie a thin string to it and try to lift it. The force exerted by the bag will hit the string harder, reaching for your plams. As the thin string has less force, its reaction force is not enough to hit back the greater force. Also, the less the surface area, the more difficult the grip gets. But, if you attach a thick rope or belt, the force exerted my the bag is automatically minimized as the reaction force of the thick rope is near about the action force. Hence, greater the surface area, better the grip.
<em>*action force: force exerted by the bag</em>
<em>*reaction force: the force hit back by the rope</em>
